1. Technical Field
The present disclosure relates to a permanent magnet synchronous machine including a rotor and a stator.
2. Description of the Related Art
Permanent magnet synchronous machines are synchronous machines including a rotor having a permanent magnet and a stator having a coil. The term “synchronous machine” is the generic term for motors, generators, and any electric machines including a combination of motors and generators. Accordingly, in the present disclosure, the term “permanent magnet synchronous machine” is not limited to one of “motor” and “generator”.
Concentrated-winding coils have been widely used in permanent magnet synchronous machines that are used in applications where reduction in the size of permanent magnet synchronous machines is needed. This is because, by using concentrated-winding coils, it is possible to reduce the length of coil ends of a stator (end portions of a coil protruding from a stator core in the axial direction) in the axial direction. In existing permanent magnet synchronous machines, the length of a core (iron core) body of a rotor in the axial direction is shorter than the length of a stator, including coil ends, in the axial direction. In this case, a space in the stator surrounded by each coil end, that is, a space on an inner peripheral side of each coil end, is an unused space.
A small and high-power permanent magnet synchronous machine has been proposed in which an overhang of a rotor is disposed in the unused space (Japanese Unexamined Patent Application Publication No. 2012-186901). Due to the presence of the overhang, the length of the rotor in the axial direction is increased, and therefore the amount of effective magnetic flux into a core body of the rotor (hereinafter referred to only as the “amount of effective magnetic flux”) is increased.
Japanese Unexamined Patent Application Publication No. 2006-211801 discloses a permanent magnet embedded motor that reduces an effect of magnetic saturation at an outer periphery of an overhang of a rotor core.